1. Field of the Invention
The present invention relates to a lithographic apparatus and a method for manufacturing a device.
2. Background Art
Lithography is widely recognized as a key processes in manufacturing integrated circuits (ICs) as well as other devices and/or structures. A lithographic apparatus is a machine, used during lithography, which applies a desired pattern onto a substrate, such as onto a target portion of the substrate. During manufacture of ICs with a lithographic apparatus, a patterning device, which is alternatively referred to as a mask or a reticle, generates a circuit pattern to be formed on an individual layer in an IC. This pattern may be transferred onto the target portion (e.g., comprising part of, one, or several dies) on the substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (e.g., resist) provided on the substrate. In general, a single substrate contains a network of adjacent target portions that are successively patterned. Manufacturing different layers of the IC often requires imaging different patterns on different layers with different reticles. Therefore, reticles must be changed during the lithographic process.
The market demands that the lithographic apparatus perform the lithography process as quickly as possible to maximize manufacturing capacity and keep costs per device low. Thus, it is preferable that changing reticles during the lithography process takes the least possible time. Unfortunately, conventional reticle exchange devices are not designed to function in a vacuum environment, and those that are designed to function in a vacuum environment are not fast enough. They also tend to exhibit problems with vacuum sealing and have a large quantity of bearings, both of which lead to further problems of outgassing and particulate contamination. Particulate contamination causes manufacturing defects which waste production capacity, time, and materials. Outgassing can contaminate lenses which reduces the effective exposure power and reduces productivity or destroys lenses entirely. This waste reduces foundry efficiency and increases fabrication expenses.